Surge protector is a lie?

I have a Micromark surge protector. Just a plug (not as in to connect an appliance, it just plugs into a socket to absorb surges, no cable comes out of it). I was interested in the LED on the front which says "protection active", so I opened it to look inside to see how it knew if it had expired. What do I find? An array of varistors as expected, but the only connection to live was through a clumsily soldered on piece of fusewire about 1-2 amps thickness. So.... it blows the fusewire as soon as there's an infinitely tiny surge, so therefore can't absorb much of it anyway? What's the point in that?

Reply to
Commander Kinsey
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Simple. When the light goes out you give Micromark more of your money...but I think you knew that.

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Well, it is probably only meant for spikes caused by things switching on and off. I did, some years ago buy a packet of Surge protection vdr devices from RS and fitted them inside plugs where there was room. One day there apparently was a lightening strike nearby, and my stuff was fine except for

1 blown 5 amp fuse on a lamp. Interestingly these vdrs specs had an amazingly small reaction time and could for a split second dump many amps, but only over around 360v ish. So it was what one might call a limiter, I suppose. Many appliances have something like this inside, I'm told but never looked. Incidentally, I had a Samsung Fax machine, many years back trashed by a lightening strike to the public telephone wires about a mile away. It just rolled out black paper, It was under warranty, and the bloke who fixed it changed the pcb saying its a common fault, now fixed by a surge suppressor on the board.

Of course if you do really get a very local strike, I have seen the result in a local factory. Every bit of electronics had its mains input circuit trashed and nearly all the internal wiring had to be replaced and the sockets were in fact blown off the wall and melted. Really a sobering thought. Brian

Reply to
Brian Gaff

I had a ground strike near me a few years ago. Apparently the surge of electricity in the ground was picked up by my satellite TV antenna's underground wire. The satellite receiver was fried AND SO WAS the UPS

  • surge control unit that the satellite receiver was plugged into. Nothing else in the house was affected.

When lightning is real close, I now unscrew the dish antenna from the receiver and just watch things that I had previously recorded.

-dan z-

Reply to
dyno dan

Allowing every lunatic to own a gun might be seen as a "civil right", but it is bit silly.

They need to know which of the constituents can't think straight.

Why bother. The NRA gets its money from gun manufacturers who want to maximise their market by selling to every half-wit who think that owning a gun is useful for self-defense, when the guns are much more frequently used by half-wits to delete themselves from the gene pool when they happen to feel depressed.

That's no loss. But some of them kill other people in the process.

<snipped access to dangerous nonsense >

A bizarre misconception. Are you sure that you aren't Flyguy posting under s new nym?

Reply to
Anthony William Sloman

Most people don't even know what a power surge is. A surge is from a nearby lightning strike, that induces current into the long lines of power and phone, just like a transformer.

People read that a $10 outlet strip can work magic and protect them from bad stuff. There's very little you can to to protect your equipment actually. The worst stuff seems to be from the phone lines, rather than the power lines. Probably because there is much less load on the phone lines, so the voltage can spike higher.

Surge protection is inherently lifespan limited. By passing the current of a surge, the power is absorbed into the protection device. Every device has limits and can be destroyed. Then you no longer have protection. A device that you plug into an outlet to protect the whole house, is inherently limited in its ability to protect, by the parasitic parameters of the house wiring. A proper device to protect the house, will be wired into the power panel where it can have maximum effect. Even then, it has to be checked after every event to see if it needs replacement.

I've only ever had problems on modem type devices. Never on anything expensive. I don't bother with these gadgets. People will talk about the appliances they've lost, but no one can show any events of protection. I just don't see where they are worth anything. They are like an elephant shield. "It's working, isn't it?"

Reply to

Cheap chinese appliances with fake UL and CE labels need fake chinese surge protectors with fake UL and CE labels.

Micromark seems to be sold in the UK but not in the US.

Reply to
John Larkin

Surge protectors are a lot cheaper than appliances like microwave, TV or computer. I had problems with all before using surge protectors. Living in a treed area, high tension line would fall onto low tension line to houses causing the voltage surge.

Reply to
invalid unparseable

This is the sort of anecdotal claims that perpetuate the use of pointless surge protectors. If you have a power line cross, that would put not just a few joules of energy into your wiring, but the full potential energy of the high voltage power lines!!! You don't have any surge protectors in your house that will prevent that "surge" from damaging equipment.

I also live in a "treed" area. Some years ago, a hurricane remnant dropped trees all over the area, including on virtually every power line. I did not suffer any damage to anything in the house, other than my olfactory sensor, because there was no running water for a week.

People often don't really understand what surges are about and feel the $10 "protector" they buy will accomplish something. It's not very likely to help in all but a few cases where the "surge" is of high enough energy to damage an appliance, but low enough energy so the protector will actually protect, and not just blow out along with the appliances.

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Sometimes, you do. Surge protectors also have a circuit breaker or fuse, and some appliances having their own internal surge protectors also have a reset button. I've done a few logic board resets for a customer who had a high-V power wiring issue, and those old Macintosh logic boards did have an internal button to reset their panic-disconnect logic. Power button didn't function, and simply unplugging the AC didn't do a reset.

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Those devices that are connected to multiple networks, such as mains, phone, CATV etc. are at greater risk and are hardest to protect. Typically each of these networks are grounded at different places. While in normal situations these grounding points are in a similar potential, but during a surge several kA can flow into only one network grounding point. Due to grounding resistance (and inductance), this current will cause a ground bounce of hundred or thousand volts on the whole network.

For example a lightning strike into phone system will cause a ground bounce at the telephone exchange elevating the whole telephone network potential. The mains network potential may be undisturbed.

If you have a device, such as modem, connected to both mains and phone network, the elevated potential on the phone network may flash over to the mains network grounding electrode, burning a lot of PCB traces on the way.

A device connected to only one network such as a passive telephone, may jump to several kV due to ground bounce without damage, since there are no paths to ground. Of course it is not a good idea to use the phone during a thunderstorm, since you may get a spark from the elevated potential of the headphone into your ear :-).

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Guessing, the varistors absorb a quick surge, and the "fuse" doesn't blow. If the surge is enough to blow the electronics and cause them to short circuit, the "fuse" blows and avoids the gadget to cause damage to the rest of the house. Of course, the spike could still blow the house, but you will not be able to sue Micromark for it.

Reply to
Carlos E.R.

Obviously, there is some complicated rationale for what was done.

If you look at a proper design, the protective components have barriers placed next to them, to contain shrapnel. And this is to prevent the protection block from becoming a flame thrower or punching holes in adjacent components.

The components are also placed in a metallic housing (for fun).

So it is possible to make a surge arrestor with some useful properties. Not all of these things need to be a joke.

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There is a single-plug entrant there, but the physical properties aren't quite as good.


Reply to

In general if you have SMPS on the rings, you have what amounts to an 8 amp + capacitor surge limiter right there and short transients wont get through the mains filters anyway.

In short if you get a surge big enough to be a problem it will take out the surge arrestors only anyway.

My time in S Africa taught me that nothing is proof against near wire strikes except physical isolation - transformer or opto coupler.

And if you get a full wire strike, all bets are off. You will be jumping across any short gap anywhere nearby.

Full carnage.

Reply to
The Natural Philosopher

I used to work with alarm systems. I was called to fix a system on top of a ridge. It was in the garage and had been the victim of a local lightning strike. The panel circuit board was fried. Once that was replaced, the loop was open, so standard procedure is to explore, looking for the point where voltage is lost. I quickly found an open in the wire itself. It had a scorch mark and a break in the wire where it ran through a hole in the joist next to the power cable. Fixed it and... still open, lather rinse, repeat. I don't recall how many opens I found. I may have given up and run a new loop wire. But whatever I did, I know I didn't run them through the same holes as the power cables and kept some distance between them.

I wonder how many volts it takes to arc through the two layers of insulation?

Reply to

Varistors usually fail short-circuit, hence the fuse. There's no point wasting money on a breaker in that position.

Reply to
Jasen Betts

HT lines generally do not cross over LV lines for this reason.

All the places where I have seen this happens there is always an additional bare copper earth line above the 3 phases and neutral, and this extra earth is connected to earth at each of the supporting poles.

These days the LV stuff is being replaced with twisted bundles of insulated aluminium cable anyway which should minimise the problem.

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I do not know about their wiring here. Service to my street is underground but above ground leads to it. In the past I recall wet branches falling causing the short between HT and LT.

Reply to
invalid unparseable

LOL! They run electric and phone and cable on the same poles. Electric is on top with phone and cable beneath. That way the phone and cable guys don't need to use HV procedures and equipment. But a cross is absolutely a possibility and procedures are in place to minimize the risk.

Higher voltage power lines are not run on the same poles as lower voltage lines, because they have different requirements for height, conductor separation and design of the structure. Also, there's no use, the two sets of wires run between different places.

There's no limit to the amount of urban myths regarding power line surges. People hear something that sounds good, now it becomes fact to them.

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Why would different voltage power lines be running on the same poles??? By "LT", do you mean phone and cable?

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